Varus angulated knees are deformities which are characterized by abnormal angulations of the leg in relation to the thigh. Stedman's Medical Dictionary, Williams & Wilkins, Baltimore, Md. (1995). For example, the genu varus angulated knee condition is characterized by an outward bowing of the legs and is commonly referred to as bowleg. Another example, the genu valgus angulated knee condition, is characterized by a lateral angulation of the leg in relation to the thigh and is commonly referred to as knock-knee. Either of these conditions may result in abnormal loads on the femurtibial joint. Further, such loads may cause tensile forces to develop in the collateral ligaments and other soft tissue structures. Persons with varus angulated knee conditions may experience knee pain, swelling, recurrent loss of stability related to activity, functional limitations, and subluxation. Both the genu varus and genu valgus angulated knee conditions may require reconstruction of the surrounding ligaments as well as correction of the abnormal angulation.
High Tibial Osteotomies (HTO) are surgical methods used to correct the abnormal angulations of varus angulated knees. Frank R. Noyes, et al., High Tibial Osteotomy in Knees with Associated Chronic Ligament Deficiencies in Master Techniques in Orthopaedic Surgery, Reconstructive Knee Surgery, 185, 185-187 (1995). In accordance with such methods, the desired angle of correction is first determined. Transverse and oblique incisions are then made into a lateral portion of the upper tibia forming a triangular-shaped opening. The opening is closed by rotating the lower portion of the tibia relative to the upper portion of the tibia so that the long axes of the lower and upper portions of the tibia are substantially aligned or slightly (e.g., 5-13 degrees valgus) over-corrected relative to the desired correction angle. A. Miniaci et al., Proximal Tibial Osteotom. A New Fixation Device, 246 Clinical Orthopaedics and Related Research 250, 250-259 (September 1989). The closure is secured with an L-shaped bracket or buttress that is screwed into the tibia on each side of the closure.
Accordingly, the HTO procedure requires shortening of the tibia and the fibula. Such shortening may lead to ankle pain. Additional incisions may also be necessary because it may be difficult to determine the amount of bone removal required.
Unilateral frame distraction procedures are alternative surgical methods for the correction of abnormal angulation of varus angulated knees. In accordance with such methods, the medial cortex of the tibia is divided leaving the medullary bone, the lateral aspect of the joint, the tibia and the peroneal nerve intact. James J. Elting, M.D. et al., Unilateral Frame Distraction: Proximal Tibial Valgus Osteotomy for Medial Gonarthritis. Vol. 27 No. 5 Contemporary Orthopaedics 435, 436 (1993). Pins or screws are placed, respectively, transversely into the proximal tibia epiphysis and into the mid-shaft region of the tibia, and used to attach the axial fixator. The purpose of the fixator is to distract the bone in order to position the tibia in the proper alignment. After surgery, the patient distracts the fixator approximately 1 millimeter per day (0.25 mm, 3 to 4 times per day) until the tibia is in the proper alignment and knee pain is relieved. Once callus formation occurs, the fixator is dynamized to encourage film bone consolidation. When the newly-formed medially based bone wedge appears mature and fully consolidated, the fixator is removed.
In contrast to one-time surgeries, the above-identified procedure may require approximately an additional three-month post-surgery distraction period to complete the correction, as well as removal of the fixator after that period. Further, during the post-surgery distraction period, the procedure may require active patient participation which may or may not be reliable. Moreover, the patient's wearing of the externally attached fixator may be cumbersome and embarrassing for the patient. In addition, whether the tibial realignment remains stable over time is not yet known.
Another surgical method for the correction of varus angulated knees involves a spacer attached to a blade plate. Dr. Ch. Mansat, The Mansat Staple Blade, Sales brochure from Societe De Protheses Othopedie Reeducation Traumatologie, Saint-Jean 31240 France. In accordance with this method, a transverse incision is made in the medial to lateral direction in the upper, medial portion of the tibia leaving the lateral cortex portion of the tibia intact. The lower portion of the tibia below the incision is positioned at a pre-determined angle to correct the varus deformity, with the intact lateral cortex of the tibia acting as a hinge. Angularly positioning the lower tibia portion separately from the upper portion of the tibia above the incision forms a triangular-shaped opening at the incision point. A square-shaped spacer attached to a blade plate is positioned in the mouth of the opening and secured with screws through the blade plate into the tibia.
In the above-identified method, a significant amount of bone growth is required to fill the opening, since the spacer has a different shape from the triangular-shaped opening formed by the surgical incisions. Further, once the spacer is properly positioned, the surgical method requires the additional step of fixing the screws of the blade plate into the tibia to secure the spacer to the bone.
Thus, there is a need for devices, kits and methods to correct varus angulated knee deformities which avoid shortening the tibia and fibula causing ankle pain. Further there is a need for devices, kits and methods which do not require the wearing of external devices and lengthy post-surgery correction periods involving potentially unreliable active patient participation. In addition, there is a need for devices and kits and methods that both promote bone growth and minimize the amount of bone growth required for correction and strengthening. Further, there is a need for varus angulated knee correction devices which are secured in the desired positions without the need for additional securing structures.